This invention relates to a urine preservative.
In monitoring the health of patients, urine is routinely collected and analyzed for analytes such as ammonia, calcium, urea nitrogen, sodium, potassium, and chloride. If the urine must be stored prior to analysis, precautionary measures should be taken to preserve the analytes in the urine. In the absence of a preservative, many analytes such as ammonia and calcium are unstable at room temperature. Other analytes are somewhat more stable. For example, urea, sodium, potassium, and chloride are stable for approximately 28 days, 7 months, 28 days, and 4 months, respectively. Although freezing the urine is a common method for preserving urine, freezing is not always a viable option. For example, in monitoring the health of crew members on board spacecraft, or patients in geographically remote areas, the availability of cold storage space typically is limited or unavailable.
Many of the previously described methods for preserving urine analytes at ambient temperatures do not preserve a broad spectrum of analytes and/or pose health risks. For example, strong acids such as concentrated hydrochloric acid and glacial acetic acid preserve few of the analytes present in urine. In spacecraft, the use of these acids is further limited because they impose a safety hazard to crew members. Furthermore, strong acids tend to alter the pH of the urine and negatively effect the analytes in urine. Other acids, such as diluted boric acid, pose few health hazards but ammonia remains unstable after treatment of urine with boric acid. Other compounds, such as thymol and thimerosal, have been used as urine preservatives; however, these compounds require special handling in order to alleviate safety concerns. In addition, ammonia remains unstable even after treatment of urine with thymol.